1. Field of the Invention
This invention relates to an automatic paper loading mechanism and method for printers, and more particularly to an improved automatic paper loading mechanism and method in which the paper supply tray is moved to a first position to load the paper into the machine and then backs away from the first position to a second position to reduce the drag on the paper once loaded, the entire movement of the paper and tray being driven by a single motor and a plurality of gears.
2. Art Background
When paper is automatically fed from a stack in a printer, as opposed to a manual feed system, the paper is typically pressed against the remainder of the stack and dragged across the stack causing undue friction. This friction may result in misalignment of the paper in the printer, which in turn results in a skewed page of print or poor vertical registration. This is particularly problematic where the printer is a high resolution type which requires exacting placement and positioning of the paper.
There are many different mechanical arrangements for the supply of paper to a printer. A common technique for feeding paper or other print media into a printer involves the use of a pinch or feed roller or rollers which are specifically dedicated to transferring the paper from a paper tray to the nip which receives the paper. From there the paper is advanced by the rollers which drive the paper to and past the printhead. A third drive is used for movement of the paper tray as required to feed subsequent pieces of paper to the nip. In sum, the printer drive assembly of the prior art requires 3 separate drives, which invariably adds to the cost of a printer and increases the risk of required repair since any of the three motors could become disabled, thereby disabling the entire system.
More recently, Hewlett-Packard in its U.S. Pat. No. 4,728,963, described a single motor system for driving both the paper and the paper tray, which system relies upon a fairly large and complex mechanical arrangement including a mechanically actuated multiplexer for initiating the conveying of a sheet of paper from the paper supply tray to the print zone. The multiplexer includes a plurality of multiplexer gears, each being actuated by a trigger mechanism which positions the gears as necessary to drive the various systems of the printer. Because of the complex gearing which takes up a substantial amount of space, such device is larger than desired.
It would be desirable to provide a printer drive system requiring only a single motor, but which has all the features and advantages of a multiple motor system. It would also be an advantage to provide a printer drive system having a paper tray retraction system operating from the same drive motor for the best results particularly in precision printing systems. It would also be desirable to provide a compact and low cost printer with good print characteristics. These and other advantages may be found in the present invention which is described in summary below.